A sunscreen cosmetic composition cuts off ultraviolet rays emitted from the sun, and therefore is used for protecting the skin from harmful damages caused by ultraviolet rays. A base type of the cosmetic composition includes an emulsion type, a lotion type, and an oil type. Of these, an oil-in-water type emulsion is widely used as it gives a moist feeling on use and can be formulated into a broad range of products including a low SPF product and a high SPF product (Non-Patent Document 1).
Meanwhile, the ultraviolet absorbent added to a sunscreen cosmetic composition is classified into an oil soluble type and a water soluble type. In this regard, to obtain high protection based on absorption of ultraviolet rays in the UVA region (wavelength of 320 to 400 nm) and UVB region (wavelength of 290 to 320 nm), it is necessary to add a UVB absorbent and a UVA absorbent with a good balance between them.
However, to improve the protection ability against ultraviolet rays by adding a large amount of an oil soluble ultraviolet absorbent, a surface active agent also needs to be used in a large amount to ensure emulsion stability. As a result, there is a tendency that a problem in use, such as oily feeling or stickiness is caused. In particular, the UVA absorbent has a problem of having lowered emulsion stability when its concentration is high in oil.
For example, it is described in Patent Document 1 that, by using polysaccharide derivatives having a specific substituent group, polyols, and a non-ionic surface active agent with HLB of 4 to 9 in combination with an oil component to stably add a material with poor solubility in an oil-in-water type emulsion composition, the emulsion particles can be more finely and homogeneously dispersed compared to conventional techniques. However, the ultraviolet absorbent is not discussed as a material with poor solubility.
In Patent Document 2, an oil-in-water type emulsion cosmetic composition which contains stably dispersed various oil components and has good feel, emollient effect and moisturizing effect on the skin by using polyoxyethylene addition type castor oil and polyoxyethylene addition type sorbitan fatty acid ester as an emulsifying agent is described. However, the ultraviolet absorbent is not discussed as an oil component to be added.
In Patent Document 3, a sunscreen composition as an emulsion containing 4,4-diaryl butadiene based ultraviolet screening agent which is prepared by adding ionic polymer particles instead of using a surface active agent, in which an oil droplet has a diameter of 500 nm or less, is described.